L-lactide polymerization – living and controlled – catalyzed by initiators: Hydroxyalkylated organic bases

Abstract

Polymerizations of l-lactide (LA) were initiated with hydroxyalkylated strong organic bases functioning simultaneously as catalysts (INICATs). Organocatalysts used until now in Ring-Opening Polymerization, particularly of l-lactide, had to be combined with separately added initiators (most often alcohols) in order to provide control of polymerization. At the conditions used in the present work, polymerizations with INICATs proceed as living and controlled. The applied INICATs are entirely incorporated into macromolecules as the end groups, as shown by MALDI-ToF-ms (MTms) and Diffusion Ordered Spectroscopy (DOSY) analyses. No side products were detected in the system after the complete monomer conversion. The presence of the initiating and catalytic functions in one molecule provides novel kinetic and mechanistic features. Besides, as it is known, conjugation of the low molar mass compounds (e.g. toxic catalysts) with polymers reduces toxicity. Therefore, the present approach may allow safe usage of modified organocatalysts, whereas the parent compounds, sometimes toxic, when left alone, may diffuse to the polymer surface.